It's the reason for the collapse of democratic choice. It's the source of our growing disillusionment with politics. It's the great unmentionable. Corporate power. The media will scarcely whisper its name. It is howlingly absent from parliamentary debates. Until we name it and confront it, politics is a waste of time.

The political role of business corporations is generally interpreted as that of lobbyists, seeking to influence government policy. In reality they belong on the inside. They are part of the nexus of power that creates policy. They face no significant resistance, from either government or opposition, as their interests have now been woven into the fabric of all three main political parties in Britain.

Most of the scandals that leave people in despair about politics arise from this source. On Monday, for instance, the Guardian revealed that the government's subsidy system for gas-burning power stations is being designed by an executive from the Dublin-based company ESB International, who has been seconded into the Department of Energy. What does ESB do? Oh, it builds gas-burning power stations.

On the same day we learned that a government minister, Nick Boles, has privately assured the gambling company Ladbrokes that it needn't worry about attempts by local authorities to stop the spread of betting shops. His new law will prevent councils from taking action.

Every week we learn that systemic failures on the part of government contractors are no barrier to obtaining further work, that the promise of efficiency, improvements and value for money delivered by outsourcing and privatisation have failed to materialise.

This policy becomes explicable only when you recognise where power really lies. The role of the self-hating state is to deliver itself to big business. In doing so it creates a tollbooth economy: a system of corporate turnpikes, operated by companies with effective monopolies.

It's hardly surprising that the lobbying bill – now stalled by the House of Lords – offered almost no checks on the power of corporate lobbyists, while hog-tying the charities who criticise them. But it's not just that ministers are not discouraged from hobnobbing with corporate executives: they are now obliged to do so.

That the words corporate power seldom feature in the corporate press is not altogether surprising. It's more disturbing to see those parts of the media that are not owned by Rupert Murdoch or Lord Rothermere acting as if they are.

For example, for five days every week the BBC's Today programme starts with a business report in which only insiders are interviewed. They are treated with a deference otherwise reserved for God on Thought for the Day. There's even a slot called Friday Boss, in which the programme's usual rules of engagement are set aside and its reporters grovel before the corporate idol. Imagine the outcry if Today had a segment called Friday Trade Unionist or Friday Corporate Critic.

This, in my view, is a much graver breach of BBC guidelines than giving unchallenged airtime to one political party but not others, as the bosses are the people who possess real power – those, in other words, whom the BBC has the greatest duty to accost. Research conducted by the Cardiff school of journalism shows business representatives now receive 11% of airtime on the BBC's 6 o'clock news (this has risen from 7% in 2007), while trade unionists receive 0.6% (which has fallen from 1.4%). Balance? Impartiality? The BBC puts a match to its principles every day.

And where, beyond the Green party, Plaid Cymru, a few ageing Labour backbenchers, is the political resistance? After the article I wrote last week, about the grave threat the transatlantic trade and investment partnership presents to parliamentary sovereignty and democratic choice, several correspondents asked me what response there has been from the Labour party. It's easy to answer: nothing.

Tony Blair and Gordon Brown purged the party of any residue of opposition to corporations and the people who run them. That's what New Labour was all about. Now opposition MPs stare mutely as their powers are given away to a system of offshore arbitration panels run by corporate lawyers.

Since Blair, parliament operates much as Congress in the United States does: the lefthand glove puppet argues with the righthand glove puppet, but neither side will turn around to face the corporate capital that controls almost all our politics. This is why the assertion that parliamentary democracy has been reduced to a self-important farce has resonated so widely over the past fortnight.

So I don't blame people for giving up on politics. I haven't given up yet, but I find it ever harder to explain why. When a state-corporate nexus of power has bypassed democracy and made a mockery of the voting process, when an unreformed political funding system ensures that parties can be bought and sold, when politicians of the three main parties stand and watch as public services are divvied up by a grubby cabal of privateers, what is left of this system that inspires us to participate?